In a person authentication, a risk of plagiarism is relatively high with use of a password authentication, an ID card authentication or the like that are widely used conventionally. And so, a biometric authentication such as a fingerprint authentication attracts attention as a person authentication having higher reliability and is being used in many situations.
In the biometric authentication, an authentication rate may be degraded because of fluctuation of biometric condition caused by chronological change from registration. This is a major cause of degradation of usability of the biometric authentication. As an example, a condition of skin changes gradually as season changes. The skin condition of many people does not change much throughout a year. Therefore, the authentication rate is not degraded throughout a year, even if a fingerprint data is registered in any season.
However, there are some people of which skin is extremely dried out in winter. In this case, the skin condition of a fingerprint data registered in summer differs largely from that of a fingerprint data registered in winter. The authentication rate may be degraded because of the difference of the skin condition. The changing of the skin condition may be changing of nick of skin, changing of skin disease, or the like in addition to the changing caused by season transition.
A method of updating registered information as necessary is supposed in order to solve the problem.
Patent Document 1 discloses a technology where time changing distribution of a similarity calculated in advance is used; it is determined that updating of registered data is needed when a predetermined condition is satisfied; and an input data for matching is registered as a new registered data.
Patent Document 2 discloses a technology where a plurality of data for matching are held at the time of matching; and a registered data is updated with use of one of data for matching held in advance.    Patent Document 1: Japanese Laid-Open Patent Publication No. 2007-11764    Patent Document 2: Japanese Laid-Open Patent Publication No. 2003-36441